The invention relates to a device for picture recording with a lighting device, having a laser light source and an optical element illuminated by this laser light source for forming the laser light, and wherein the optical element is illuminated by a dispersing lens arranged between the laser light source and the optical element the preamble to patent claim 1.
The invention is used with image sensors in the field of robotics, navigational systems and monitoring systems. A semiconductor laser, preferably expanded in one direction, is the preferred light source for such sensors. The camera used is preferably a charge-coupled device (CCD) camera with an electronically controlled shutter. Optical filters, installed in front of the camera objective, will filter out the light reflected by the illuminated object from the surrounding visible and infrared light, so that it is essentially the laser light that is processed into an image in the camera.
If a laser is used as a light source, the regulations for preventing accidents caused by laser radiation must be observed. Given the expanded radiation of the laser light and a wavelength of 750-850 nm, e.g., for a GaAs laser, these regulations only permit a laser output of 50-100 mW in order to stay within the maximum permissible radiation for laser light affecting the eye retina.
An arrangement for recording pictures is described in the German Unexamined Published Patent application No. P43 35 244. The laser output for this arrangement is distributed such that a point image of the laser light source cannot be formed with an optical system that is located in the illumination range, e.g., the human eye, if applicable with auxiliary means. This does not detract from the illumination characteristics of the lighting device, e.g. through generating a fan-shaped light bundle. In addition, the US 4 971 415 A and JP 60 193 140 disclose circular-arc type arrangements of several semiconductor lasers.
It is the object of the invention to provide a lighting device for recording pictures, which makes it possible to maintain the maximum permissible radiation for laser outputs exceeding 1 W over the total illumination range, has good spatial resolution characteristics and a high picture frequency, and can be produced with a compact design.